public static function find_by_sku($sku)
 {
     include WCAPIDIR . "/_globals.php";
     $product = new Product();
     $product->setValid(false);
     $pid = $wpdb->get_var($wpdb->prepare("SELECT post_id FROM {$wpdb->posts} WHERE post_title = %s' LIMIT 1", $sku));
     if ($pid) {
         $product = Product::find($pid);
     }
     return $product;
 }